In this introduction to the Special Issue "Empirical Studies on Investment Disputes", we offer a new heuristic model to structure the thinking about investment arbitration. Investment arbitration is presented here as a political system in a sense inspired by David Easton's landmark theory: it transforms the input of key actors (namely states, investors, arbitrators, and arbitration institutions) into output (namely arbitral awards taken in the aggregate), with feedback loops from output to input, leading to or calling for adjustments or other reactions from these actors. We use this model to review some of the leading existing research and bring together key insights offered by the contributions to the issue.